JVM 心得分享(加载 链接 初始化)

 package com.chong.studyparalell.clazz.loader;

public class ClassLoaderDemo {
public static void main(String []args){
Test test2 = new Test();

System.out.println("Test2实例化结束"+test2.toString());

}
}

package com.chong.studyparalell.clazz.loader;

public class Test{

private static Test test1 = new Test();
private static int a = 2;
private static int b = 2;

static {
System.out.println("【Test类静态块】a=" + a);
}

public Test(){

System.out.println("【Test类构造方法】a=" + a);
System.out.println("【Test类构造方法】b=" + b);
System.out.println("【Test类实例】" + this.toString());
}

public static Test newInstance(){
return test1;
}
}

package com.chong.studyparalell.clazz.loader;

public class TestBase {

private static int base_a = 2;
private static int base_b = 2;

static {
System.out.println("【父类静态块】 base_a="+base_a);
}

public TestBase(){
System.out.println("【父类 构造方法】base_a=" + base_a);
System.out.println("【父类 构造方法】base_b=" + base_b);
System.out.println("【父类 实例】"+ this.toString());
}

}

package com.chong.studyparalell.clazz.loader;

public class Test extends TestBase{
内容同第一步；
}

 package com.chong.studyparalell.clazz.loader;


public class MyClassLoaderPilot {

public static void main(String[] args) {

try {
MyClassLoader classLoader = new MyClassLoader();
String filename = "com.chong.studyparalell.demon.DemonThreadDemo";

Object clazz = classLoader.loadCustomizeClass(filename);
System.out.println(clazz);

} catch (Exception e) {
e.printStackTrace();
}
}

}

package com.chong.studyparalell.clazz.loader;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class MyClassLoader extends ClassLoader {

private String demoPath = "D:worktemp";

public Class loadCustomizeClass(String filename) throws ClassNotFoundException {

FileInputStream fis = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
// 1.获取class文件的字节码（二进制数据）
String[] fileNames = filename.split(".");
fis = new FileInputStream(demoPath + fileNames[fileNames.length-1] +".class");
byte[] bytes = new byte[1024];
int len = 0;
while ((len = fis.read(bytes)) != -1) {
baos.write(bytes, 0, len);
}

} catch (Exception e) {
throw new ClassNotFoundException();
} finally {
try {
fis.close();
} catch (IOException e) {
throw new ClassNotFoundException();
}
}

byte[] paramArrayOfByte = baos.toByteArray();
// 2。把二进制文件定义为class对象返回
return defineClass(filename, paramArrayOfByte, 0, paramArrayOfByte.length);
}
}

class com.chong.studyparalell.demon.DemonThreadDemo